Light emitting device, light emitting system having the same, and fabricating method of the light emitting device and the light emitting system

ABSTRACT

A semiconductor device includes a first light emitting chip, the first light emitting chip having a first semiconductor layer, a second semiconductor layer, and a first active layer disposed therebetween, a second light emitting chip disposed on the first light emitting chip, the second light emitting chip having a third semiconductor layer, a fourth semiconductor layer, and a second active layer disposed therebetween, and a conductive layer disposed between the first semiconductor layer and the fourth semiconductor layer, the first semiconductor layer and the fourth semiconductor layer having different conductivity types.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean patent applications2008-0076549 filed on Aug. 5, 2008, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a light emitting device and a methodof forming the same, and more particularly to a light emitting devicecomprising at least two stacked light emitting diode chips and a methodof forming the same.

DISCUSSION OF RELATED ART

A light emitting diode (LED) is a p-n junction diode that emits light asa result of direct radiative recombination of excess electron-holepairs. When the LED is forward biased, electrons are able to recombinewith holes and energy is released in the form of light. The color oflight emitted is based on the band gap energy of the materials formingthe p-n junction.

An LED can operate on direct current (DC) power or alternating current(AC) power. Light emitting efficiency of the AC LED per unit area ishalf of the DC LED, because in the AC power operation when two diodesare connected in parallel one of the two diodes is alternately turnedon. Thus, one way to increase the light emitting efficiency in ACoperated LED is to stack one LED chip over another. It would appear thatan LED is always on because one of the two stacked LED chips will be on.Conventionally, LED chips are stacked one on top of another, separatedby an insulating layer. To connect the stacked LED chips to an AC powersource, extraneous wiring around the insulator may be needed.

A need therefore exists for an AC-operated light emitting deviceproviding high light emitting efficiency per unit area.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a light emittingdevice having at least two LED chips stacked one over another. The lightemitting device can operate on the AC power. The two LED chips areelectrically connected through a conductive material disposedtherebetween. As such, a number of electrodes and wires connecting thetwo LED chips can be minimized.

According to an exemplary embodiment of the present invention, asemiconductor device comprises a first light emitting chip, the firstlight emitting chip having a first semiconductor layer, a secondsemiconductor layer, and a first active layer disposed therebetween, asecond light emitting chip disposed on the first light emitting chip,the second light emitting chip having a third semiconductor layer, afourth semiconductor layer, and a second active layer disposedtherebetween, and a conductive layer disposed between the firstsemiconductor layer and the fourth semiconductor layer, the firstsemiconductor layer and the fourth semiconductor layer having differentconductivity types.

The semiconductor device may further comprise a first electrode disposedon the conductive layer, a second electrode disposed on the thirdsemiconductor layer, and a third electrode disposed on the secondsemiconductor layer.

The second electrode and the third electrode can be electricallyconnected.

The semiconductor device may further comprise a substrate disposed onthe second semiconductor layer.

The substrate may comprise at least one of a semiconductor material or aconductive material.

The conductive layer can be transparent.

The conductive layer can be reflective.

The third electrode can be reflective.

The third electrode may include a reflective side wall.

The third electrode can be flat.

The semiconductor device may further comprise vias disposed between thefourth semiconductor layer and the conductive layer.

The second light emitting chip is can be a vertical type light emittingchip.

The semiconductor device may further comprise a third light emittingchip including a fifth semiconductor layer, the fifth semiconductorlayer disposed on the third semiconductor layer, the fifth semiconductorlayer and the third semiconductor layer having different conductivetypes.

The semiconductor device may further comprise a third light emittingchip including a fifth semiconductor layer, the fifth semiconductorlayer disposed on the third semiconductor layer, the fifth semiconductorlayer and the third semiconductor layer having the same conductive type.

The first and second light emitting chips can be configured to bealternately energized on respective alternating halves of an AC waveformto emit light.

A contour of the first light emitting chip overlapping the second lightemitting chip can be substantially the same as a contour of the secondlight emitting chip.

According to an exemplary embodiment of the present invention, asemiconductor device comprises a first pad and a second pad disposed ona first surface of a first substrate, a first light emitting chipdisposed on the first surface of the first substrate, the first lightemitting chip having a first semiconductor layer, a second semiconductorlayer electrically connected to the second pad, and a first active layerdisposed between the first and second semiconductor layers, a secondlight emitting chip disposed on the first light emitting chip, thesecond light emitting chip having a third semiconductor layer, a fourthsemiconductor layer, and a second active layer disposed therebetween, aconductive layer disposed between the first semiconductor layer and thefourth semiconductor layer, the first semiconductor layer and the fourthsemiconductor layer having different conductivity types, a first wireconnecting the first pad and a first electrode disposed on theconductive layer, and a second wire connecting the second pad and asecond electrode disposed on the third semiconductor layer.

The semiconductor device may further comprise a third electrode disposedon the second semiconductor layer.

The semiconductor device may further comprise a second substrate on thesecond semiconductor layer, the second substrate comprising asemiconductor material.

The conductive layer can be transparent.

The conductive layer can be reflective.

The second light emitting chip can be a vertical type emitting chip.

The first and second light emitting chips can be configured to bealternately energized on respective alternating halves of an AC waveformto emit light.

The semiconductor device may further comprise an encapsulantencapsulating the first and second light emitting chips.

The semiconductor device may further comprise a light convertingmaterial disposed in the encapsulant.

The semiconductor device may further comprise a third pad and a fourthpad disposed on a second surface of the first substrate, wherein thethird pad is electrically connected to the second pad and the fourth padis electrically connected to the first pad.

The semiconductor device may further comprise a first via disposedbetween the third pad and the second pad, and a second via disposedbetween the first pad and the fourth pad.

According to an exemplary embodiment of the present invention, a methodof forming a semiconductor device comprises forming a firstsemiconductor layer, a second semiconductor layer, and a first activelayer disposed therebetween on a first substrate, disposing a secondsubstrate on the second semiconductor layer, removing the firstsubstrate, forming a third semiconductor layer, a fourth semiconductorlayer, and a second active layer disposed therebetween on a thirdsubstrate, disposing the first semiconductor layer on the fourthsemiconductor layer, and removing the third substrate.

The method may further comprise forming a conductive layer on the firstsemiconductor layer.

The method may further comprise forming a bonding between the conductivelayer and the fourth semiconductor layer.

The method may further comprise forming a first electrode on theconductive layer, a second electrode on the third semiconductor layer,and a third electrode on the second semiconductor layer.

The third electrode can be reflective.

The conductive layer can be transparent.

According to an exemplary embodiment of the present invention, a methodof forming a semiconductor device comprises preparing a first lightemitting chip having a first semiconductor layer, a second semiconductorlayer, and a first active layer disposed therebetween, preparing asecond light emitting chip having a third semiconductor layer, a fourthsemiconductor layer, and a second active layer disposed therebetween,and disposing the first semiconductor layer on fourth semiconductorlayer to be electrically connected to each other, the firstsemiconductor layer and the fourth semiconductor layer having differentconductivity types.

The method may further comprise a conductive layer disposed on the firstsemiconductor layer.

The method may further comprise forming a first electrode on theconductive layer, a second electrode on the third semiconductor layer,and a third electrode on the second semiconductor layer.

The third electrode can be reflective.

The conductive layer can be transparent.

The method may further comprise preparing a first substrate having afirst pad and a second pad, and connecting the second electrode and thesecond pad and connecting the first electrode and the first pad.

The method may further comprise encapsulating the first light emittingchip and the second light emitting chip in an encapsulant.

The method may further comprise comprising disposing a light convertingmaterial in the encapsulant.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the present invention can be understood in moredetail from the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1(A) and FIG. 1(B) show a biased light emitting device according toan exemplary embodiment of the present invention;

FIG. 2 (A) and FIG. 2(B) show a circuit diagram of a biased lightemitting device according to an exemplary embodiment of the presentinvention;

FIG. 3 shows a light emitting device according to an exemplaryembodiment of the present invention;

FIG. 4 shows a light emitting device according to an exemplaryembodiment of the present invention;

FIG. 5 shows a light emitting device according to an exemplaryembodiment of the present invention;

FIG. 6 shows a circuit diagram of a light emitting device according toan exemplary embodiment of the present invention;

FIGS. 7(A), 7(B) and 7(C) show circuit diagrams of light emittingdevices according to exemplary embodiments of the present invention;

FIG. 8 shows a semiconductor package according to an exemplaryembodiment of the present invention;

FIG. 9 shows a semiconductor package according to an exemplaryembodiment of the present invention;

FIG. 10 shows a luminous package according to an exemplary embodiment ofthe present invention;

FIG. 11 shows a luminous package according to an exemplary embodiment ofthe present invention;

FIG. 12 shows a luminous package according to an exemplary embodiment ofthe present invention;

FIG. 13 shows an array of light emitting devices according to anexemplary embodiment of the present invention;

FIG. 14 shows a light emitting device in a package according to anexemplary embodiment of the present invention;

FIG. 15 shows a light emitting device in a package according to anexemplary embodiment of the present invention;

FIG. 16 shows a system including a light emitting device according to anexemplary embodiment of the present invention;

FIG. 17 shows a system including a light emitting device according to anexemplary embodiment of the present invention;

FIG. 18 shows a system including a light emitting device according to anexemplary embodiment of the present invention;

FIG. 19 shows a system including a light emitting device according to anexemplary embodiment of the present invention;

FIG. 20 shows a system including a light emitting device according to anexemplary embodiment of the present invention; and

FIGS. 21(A), 21(B), 22(A), 22(B), 23(A), 23(B), 24, 25(A), 25(B), 26,and 27 show a method of forming a light emitting device according to anexemplary embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings in which example embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element, or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the exemplary embodiments.

Spatially relative terms, such as “beneath”, “below”, “bottom”, “lower”,“above”, “top”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly. Also, as usedherein, “vertical” refers to a direction that is substantiallyorthogonal to a horizontal direction.

Example embodiments are described herein with reference to cross-sectionillustrations that are schematic illustrations of idealized embodiments(and intermediate structures). As such, variations from the shapes ofthe illustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments should not beconstrued as limited to the particular shapes of regions illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe present invention.

FIG. 1(A) and FIG. 1(B) show a biased light emitting device according toan exemplary embodiment of the present invention. FIG. 2 (A) and FIG.2(B) show circuit diagrams of a biased light emitting device accordingto an exemplary embodiment of the present invention.

Referring to FIG. 1(A) and FIG. 1(B), a light emitting device 20includes a first light emitting chip 110, a second light emitting chip160, first, second and third ohmic contact layers 142, 168 and 130,first, second and third electrodes 150, 170 and 140, and a substrate200. The first light emitting chip 110 is disposed on the substrate 200with an intermediate layer 210 disposed therebetween. The second lightemitting chip 160 is disposed on the first light emitting chip 110 withthe ohmic contact layers 142, 168 therebetween.

The first light emitting chip 110 includes a first semiconductor layer112, a second semiconductor layer 116, and a first active layer 114disposed therebetween. The second light emitting chip 160 includes athird semiconductor layer 162, a fourth semiconductor layer 166, and asecond active layer 164 disposed therebetween. In an exemplaryembodiment, the first semiconductor layer 112 comprises an n-typesemiconductor, the second semiconductor layer 116 comprises a p-typesemiconductor, the third semiconductor layer 162 comprises an n-typesemiconductor, and the fourth semiconductor layer 166 comprises a p-typesemiconductor. As such, the first semiconductor layer 112 and the fourthsemiconductor layer 166 have different conductivity types.

The first electrode 150 is disposed on the first ohmic contact layer142. The second electrode 170 is disposed on the third semiconductorlayer 162. The third electrode 140 is disposed on the secondsemiconductor layer 116 with the third ohmic contact layer 130 disposedtherebetween. As such, in an exemplary embodiment, the firstsemiconductor layer 112 and the fourth semiconductor layer 166 havingdifferent conductivity types are electrically connected through thefirst and second ohmic contact layers 142, 168. The second electrode 170and the third electrode 140 can be electrically connected.

The substrate 200 comprises, for example, a semiconductor material or aconductive material. The intermediate layer 210 can be disposed on thesubstrate 200. The intermediate layer 210 can comprise, for example, atleast one of Au, Ag, Pt, Ni, Cu, Sn, Al, PB, Cr, or Ti. The thirdelectrode 140 can be disposed on the intermediate layer 210. The thirdohmic contact layer 130 can be disposed on the third electrode 140. Thesecond semiconductor layer 116 can be disposed on the third ohmiccontact layer 130 and an insulator 120.

In an exemplary embodiment, a conductive layer including the first andsecond ohmic contact layers 142 and 168 can be transparent.Alternatively, the first and second ohmic contact layers 142 and 168 canbe reflective. In an exemplary embodiment, the third electrode 140 canbe reflective. The third electrode 140 can include a reflective sidewall141. The reflective sidewall 141 is inclined to increase the lightemission of the light emitting device 20. A groove 118 can be formed dueto the inclined reflective sidewall 141. In an exemplary embodiment, thethird electrode 140 can have a high reflectivity to further increase thelight emission. The reflective sidewall 141 can be omitted according toan exemplary embodiment of the present invention. As such, in anexemplary embodiment, the third electrode 140 can be flat with respectto the major axis of the substrate 200.

In an exemplary embodiment, the second light emitting chip 160 can be avertical type structure, and the first light emitting chip 110 can be avertical, lateral or flip type structure. In an exemplary embodiment,the second light emitting chip 160 and the first light emitting chip 110disposed under and overlapping the second light emitting chip 160 have asubstantially same contour.

Referring to FIGS. 1(A), 1(B), 2(A) and 2(B), the first and second lightemitting chips 110, 160 are configured to be alternately energized onrespective alternating halves of an AC waveform to emit light.

Referring to FIGS. 1(A) and 2(A), the substrate 200 and the secondelectrode 170 have a same potential. For example, a negative voltage (−)is applied to the first electrode 150, and a positive voltage (+) isapplied to the substrate 200 and the second electrode 170. As such, thefirst light emitting chip 110 is forward biased and the second lightemitting chip 160 is reversed biased. Thus, only the first lightemitting chip 110 turns on and emits light L1. The third electrode 140can reflect light generated from the first active layer 114 of the firstlight emitting chip 110. The reflected light from the third electrode140 and directly incident light from the first active layer 114 can beemitted to the outside of the light emitting device 20 through the firstand second ohmic contact layers 142, 168 when the ohmic contact layers142, 168 are transparent.

Referring to FIGS. 1(B) and 2(B), the substrate 200 and the secondelectrode 170 have a same potential. For example, a positive voltage (+)is applied to the first electrode 150, and a negative voltage (−) isapplied to the substrate 200 and the second electrode 170. As such, thesecond light emitting chip 160 is forward biased and the first lightemitting chip 110 is reverse biased. Thus, only the second lightemitting chip 160 turns on and emits light L2. The third electrode 140can reflect light generated from the second active layer 164 of thesecond light emitting chip 160. The reflected light from the thirdelectrode 140 and directly incident light from the second active layer164 can be emitted to the outside of the light emitting device 20. Thereflected light can transmit through the first and second ohmic contactlayers 142, 168 when the ohmic contact layers 142, 168 are transparent.

FIG. 3 shows a light emitting device 21 according to an exemplaryembodiment of the present invention. Referring to FIG. 3, the secondlight emitting chip 160 is disposed on a conductive layer 144. The firstelectrode 150 can be disposed on the conductive layer 144. In anexemplary embodiment, the third electrode 140 is flat. That is, thethird electrode 140 does not have an inclined side wall. As such, lightgenerated from the first light emitting chip 110 can be escaped in ahorizontal direction. When the conductive layer 144 is transparent,light generated from the second light emitting chip 160 can transmitthrough the conductive layer 144 and can be reflected by the thirdelectrode 140. When the conductive layer 144 is reflective, lightgenerated from the second light emitting chip 160 can be reflected bythe conductive layer 144.

FIG. 4 shows a light emitting device 22 according to an exemplaryembodiment of the present invention. Referring to FIG. 4, the firstlight emitting chip 110 is disposed on a first substrate 201, and theconductive layer 144 is disposed on the first light emitting chip 110.The second light emitting chip 160 is disposed on a second substrate202. A plurality of through vias 204 are disposed in the secondsubstrate 202. As such, the fourth semiconductor layer 166 can beelectrically connected to the conductive layer 144 through the throughvias 204 filled with a conductive material. The first light emittingchip 110 includes the first semiconductor layer 112, the first activelayer 114 and the second semiconductor layer 116. The secondsemiconductor layer 116 can be disposed on the first substrate 201. Thesubstrates 201, 202 may comprise a sapphire (Al₂O₃), ZnO or SiC. In anexemplary embodiment, a reflective layer can be disposed between thesecond semiconductor layer 116 and the first substrate 201. The firstelectrode 150 is disposed on the conductive layer 144. The secondelectrode 170 is disposed on the third conductive layer 162. The thirdelectrode 140 is disposed on an edge of the second semiconductor layer116. As such, in this exemplary embodiment, the second light emittingchip 160 is a vertical type, and the first light emitting chip 110 is alateral type.

FIG. 5 shows a light emitting device 23 according to an exemplaryembodiment of the present invention. FIG. 6 shows a circuit diagram of alight emitting device according to an exemplary embodiment of thepresent invention. Referring to FIGS. 5 and 6, a third light emittingchip 180 and a fourth light emitting chip 190 are stacked on the firstand second light emitting chips 110, 160. The third light emitting chip180 includes a fifth semiconductor layer 186, a third active layer 184,and a six semiconductor layer 182. The fifth semiconductor layer 186 isdisposed on the third semiconductor layer 162 with a second conductivelayer 146 disposed therebetween. In an exemplary embodiment, the fifthsemiconductor layer 186 and the third semiconductor layer 162 havedifferent conductive types. Alternatively, the fifth semiconductor layer186 and the third semiconductor layer 162 have a same conductive type.

The fourth light emitting chip 190 includes a seventh semiconductorlayer 192, a fourth active layer 194, and an eighth semiconductor layer196. The seventh semiconductor layer 192 is disposed on the eighthsemiconductor layer 196 with the fourth active layer 194 disposedtherebetween. The eighth semiconductor layer 196 contacts a thirdconductive layer 148 disposed thereunder. The third conductive layer 148is disposed on and contacts the sixth semiconductor layer 182. The sixthsemiconductor layer 182 is disposed on the fifth semiconductor layer 186with the third active layer 184 disposed therebetween. The fifthsemiconductor layer 186 is disposed on and contacts the secondconductive layer 146. The second conductive layer 146 is disposed on andcontacts the third semiconductor layer 162. The third semiconductorlayer 162 is disposed on the fourth semiconductor layer 166 with thesecond active layer 164 disposed therebetween. The fourth semiconductorlayer 166 is disposed on and contacts the first conductive layer 144.The first conductive layer 144 is disposed on and contacts the firstsemiconductor layer 112. The first semiconductor layer 112 is disposedon the second semiconductor layer 116 with the first active layer 114disposed therebetween. The second semiconductor layer 116 is disposed onand contacts the third electrode 140. The third electrode 140 isdisposed on and contacts the intermediate layer 210. The intermediatelayer 210 is disposed on and contacts the substrate 200.

The first electrode 150 is disposed on the first conductive layer 144.The second electrode 170 is disposed on the second conductive layer 146.The third electrode 140 can be disposed between the second semiconductorlayer 116 and the intermediate layer 210. The fourth electrode 188 canbe disposed on the third conductive layer 148. The fifth electrode 198can be disposed on the seventh semiconductor layer 192. In an exemplaryembodiment, the first, third, fifth and the eighth semiconductor layers112, 162, 186 and 196 can be n-type semiconductor layers, and thesecond, fourth, sixth and seventh semiconductor layers 116, 166, 182,and 192 can be p-type semiconductor layers.

Referring to FIG. 6, n numbers of luminous diodes can be stackedaccording to an exemplary embodiment of the present invention. A firstgroup for light emitting may include light emitting chips 110 and 180,and a second group for light emitting may include light emitting chips160 and 190. When a DC bias is applied, the first group or the secondgroup can turn on. That is, in an exemplary embodiment, the lightemitting device 23 can be DC biased.

In an exemplary embodiment, a combined luminous area of the first andfourth light emitting chips 110, 190 can be substantially same with acombined luminous area of the second and third light emitting chips 160,180. Accordingly, a uniform light emitting intensity can be produced.

FIGS. 7(A), 7(B) and 7(C) show circuit diagrams of light emittingdevices according to exemplary embodiments of the present invention.Referring to FIGS. 7(A), a light emitting device 24 includes a firstluminous diode group A including a plurality of sub luminous diodes, andsecond luminous diode group B including a plurality of sub luminousdiodes. Referring to FIG. 7(B), a light emitting device 25 includes afirst luminous diode group C including a plurality of sub luminousdiodes and a second luminous diode D. Referring to FIG. 7(C), a lightemitting device 26 includes a first light emitting diode E and a secondlight emitting diode group F including a plurality of sub luminousdiodes. As such, multiple light emitting diode chips can be employedaccording to exemplary embodiments of the present invention.

FIG. 8 shows a semiconductor package according to an exemplaryembodiment of the present invention. Referring to FIG. 8, asemiconductor package 31 includes the light emitting device 20, asubstrate 300 such as a printed circuit board (PCB), a first conductivepad 320, a second conductive pad 310, a first wire 330, and a secondwire 340. The first conductive pad 320 and the second conductive pad 310are disposed on the substrate 300. The first wire 330 connects the firstconductive pad 320 and the first electrode 150 disposed on theconductive layer 142. The second wire 340 connects the second contactpad 310 and the second electrode 170 disposed on the third semiconductorlayer 162.

FIG. 9 shows a semiconductor package according to an exemplaryembodiment of the present invention. Referring to FIG. 9, asemiconductor package 32 includes the light emitting device 20, thesubstrate 300 such as the PCB, the first conductive pad 320, the secondconductive pad 310, the third conductive pad 312, the fourth conductivepad 322, the first wire 330 and the second wire 340. The substrate 300comprises a plurality of first vias 316 disposed between the secondconductive pad 310 and the third conductive pad 312, and a plurality ofsecond vias 326 disposed between the first conductive pad 320 and thefourth conductive pad 322. The first and second conductive pads 320 and310 are disposed on a first surface of the substrate 300, and the thirdand fourth conductive pads 312 and 322 are disposed on a second surfaceof the substrate 300. The first pad 320 can be electrically connected tothe fourth pad 322 through the second vias 326, and the second pad 310can be electrically connected to the third pad 312 through the firstvias 316. The first and second vias 316, 326 can be a thermal pathand/or a conductor according to an exemplary embodiment of the presentinvention.

FIG. 10 shows a luminous package according to an exemplary embodiment ofthe present invention. Referring to FIG. 10, a luminous package 33includes the semiconductor package 31 encapsulated by a firstencapsulant 342. A light converting material such as, for example,phosphor 344 can be disposed in the first encapsulant 342. In anexemplary embodiment, the phosphor 344 can be dispersed substantiallyevenly throughout the first encapsulant 342. A second encapsulant 350can be disposed on the first encapsulant 342. The phosphor 344 canconvert a portion of light generated from the first and second lightemitting chips 110 and 160. For example, white light can be generatedfrom the luminous package 33 when the semiconductor package 31 generatesblue light and the phosphor 344 comprises a yellow fluorescent material.In an exemplary embodiment, red phosphor can be included to increase aColor Rendering Index (CRI). When the semiconductor package 31 generatesUltraviolet (UV) light, the phosphor 344 can comprise an RGB fluorescentmaterial. The second encapsulant 350 can prevent the phosphor 344 fromdamage caused by, for example, moisture. The first and secondencapsulant can be, for example, an epoxy, silicone, rigid silicone,urethane, oxethane, acryl, poly-carbonate, and polymide. The phosphor344 may comprise, for example, a nitride/oxide material activated bylanthanide.

FIG. 11 shows a luminous package according to an exemplary embodiment ofthe present invention. Referring to FIG. 11, a luminous package 34includes the semiconductor package 31 encapsulated by the encapsulant350. In an exemplary embodiment, the phosphor 344 can be disposed on thesubstrate 300, first and second conductive pads 320 and 310, first andsecond electrodes 150 and 170, and the third semiconductor layer 162.The phosphor 344 can be a single layer in an exemplary embodiment.

FIG. 12 shows a luminous package according to an exemplary embodiment ofthe present invention. Referring to FIG. 12, a luminous package 35includes the semiconductor package 31 encapsulated by the firstencapsulant 342 and the second encapsulant 350. In an exemplaryembodiment, the phosphor 344 can be disposed for example, conformally,on the first encapsulant 342. The phosphor 344 can be a single layer inan exemplary embodiment.

FIG. 13 is a plan view showing a luminous package module 36 according toan exemplary embodiment of the present invention. Referring to FIG. 13,the first conductive pad 320 is disposed adjacent to the secondconductive pad 310 in a first column. In a second column next to thefirst column, another first conductive pad 320 and second conductive pad310 are disposed. As such, a plurality of columns including the firstand second conductive pads 320 and 310 are disposed to form a packagearray. In the first column, the second light emitting chip 160 isdisposed on the first light emitting chip 110. The second electrode 170is disposed on the second light emitting chip 160. The first electrode150 is disposed on the first light emitting chip 110. The first wire 330connects the first electrode 150 and the first conductive pad 320. Thesecond wire 340 connects the second electrode 170 and the secondconductive pad 310.

FIG. 14 is a perspective view showing a luminous package moduleaccording to an exemplary embodiment of the present invention. In afirst column, a plurality of light emitting devices 20 disposed on thesubstrate 300 are arranged, for example, in a regular interval. Theplurality of light emitting devices 20 are encapsulated by the first andsecond encapsulants 342 and 350 having an elongated tube shape cut inhalf. A second column including the plurality of light emitting devices20 and the first and second encapsulants 342 and 350 can be disposednext to the first column with an interval therebetween. In thisexemplary embodiment, more than one light emitting device 20 can beencapsulated by the first and second encapsulants 342 and 350.

FIG. 15 is a perspective view showing a luminous package moduleaccording to an exemplary embodiment of the present invention. In afirst column, a plurality of light emitting devices 20 disposed on thesubstrate 300 are arranged, for example, in a regular interval. Each ofthe plurality of light emitting devices 20 is respectively encapsulatedby the first and second encapsulants 342 and 350. In an exemplaryembodiment, the first and second encapsulants 342 and 350 can be asubstantially hemisphere shape.

FIG. 16 is a cross-sectional view of a backlight unit according to anexemplary embodiment of the present invention. In an exemplaryembodiment, an edge type backlight unit can be used. The light emittingdevice 20 disposed on the substrate 300 is located at an edge of a lightguiding plate 400. The light guiding plate 400 includes a transfer sheet410 disposed on a reflective sheet 412. A plurality of reflectivepatterns 412 a can be disposed on the reflective sheet 412. A displaypanel 450 can be disposed on a spreading sheet 414 with prism sheets 416positioned therebetween. The spreading sheet 414 spreads light receivedfrom the light guiding plate 400 and can be disposed on the lightguiding plate 400. The prism sheets 416 can comprise two sheets andguide light to the display panel 450 in an orthogonal direction.

FIGS. 17, 18, 19 and 20 are systems using a light emitting deviceaccording to exemplary embodiments of the present invention. Referringto FIG. 17, the light emitting device is used in connection with aprojector. The projector includes a light source 410, a condensing lens420, a color filter 430, a sharpening lens 440, and a digitalmicromirror device (DMD) 450 arranged in a substantially in a line. Amicrolens 480 receives light from the DMD 450 and projects an image onthe screen 490. Referring to FIG. 18, a plurality of luminous packages 1are used as a light source for a vehicle 500. Referring to FIG. 19, aluminous package 1 according to an exemplary embodiment is used as alight source for a street lamp 600. Referring to FIG. 20, the pluralityof luminous packages 1 according to an exemplary embodiment is used as alight source for an illumination lamp 700.

FIGS. 21 through 27 show a method of forming a light emitting deviceaccording to an exemplary embodiment of the present invention.

Referring to FIG. 21(A), a first preliminary semiconductor layer 112 ais formed on the first substrate 100. The second preliminarysemiconductor layer 116 a can be formed on the first preliminarysemiconductor layer 112 a with a first preliminary active layer 114 adisposed therebetween. In an exemplary embodiment, a buffer layer can beformed between the first semiconductor layer 112 a and the firstsubstrate 100. The buffer layer can increase crystal characteristics ofthe first preliminary semiconductor layer 112 a, the first preliminaryactive layer 114 a, and the second preliminary semiconductor layer 116a.

The first preliminary semiconductor layer 112 a, the first preliminaryactive layer 114 a, and the second preliminary semiconductor layer 116 acan comprise In_(x)Al_(y)Ga(1−x−y)N (0≦x≦1, 0≦y≦1) such as, for example,AlGaN or InGaN. The preliminary semiconductor layers 112 a and 116 a canbe formed on the first substrate 100 by, for example, metal organicchemical vapor deposition (MOCVD), liquid phase epitaxial growth,hydride vapor phase epitaxial growth, molecular beam epitaxial growth ormetal organic vapor phase epitaxial growth. When the first preliminarysemiconductor layer 112 a is a first conductive type, the secondpreliminary semiconductor layer 116 a can be a second conductive type.For example, when the first preliminary semiconductor layer 112 a is ann-type semiconductor layer, the second preliminary semiconductor layer116 a can be a p-type semiconductor layer. For example, when the firstpreliminary semiconductor layer 112 a is a p-type semiconductor layer,the second preliminary semiconductor layer 116 a can be an n-typesemiconductor layer.

In the preliminary active layer 114 a, light recombination betweenelectrons and holes occurs. The preliminary active layer 114 a cancomprise at least one potential well and a potential barrier. To adjustlight emitting characteristics, at least one of B, P, Si, Mg, Zn and Secan be doped in the potential well and/or the potential barrieraccording to an exemplary embodiment of the present invention.

A heat treatment of about 400° C. can be performed to activate thesecond preliminary semiconductor layer 116 a. For example, the secondpreliminary semiconductor 116 a can have improved p-type characteristicsthrough the heat treatment when the second preliminary semiconductorlayer 116 a is In_(x)Al_(y)Ga(1−x−y)N doped with Mg because H bonded toMg can be separated from the Mg. In an exemplary embodiment, the firstsubstrate 100 may comprise a dielectric material such as, for example,sapphire (Al₂O₃), ZnO or a conductor such as, for example, a Si or SiC.

Referring to FIG. 21(B), the first active layer 114, the firstsemiconductor layer 112, the second semiconductor layer 116, and agroove 118 can be formed by patterning the first preliminarysemiconductor layer 112 a, the first preliminary active layer 114 a, andthe second preliminary semiconductor layer 116 a. The groove 118 hasinclined surfaces which can be used to reflect light emitted from theactive layers 114 and 164 according to an exemplary embodiment of thepresent invention.

Referring to FIG. 22(A), an insulator 120 can be formed on the first andsecond semiconductor layers 112 and 116 and the active layer 114. Thatis, the insulator 120 can be conformally formed on the recessed andprotruding portion of the first light emitting chip 110. A part of thetop surface of the second semiconductor layer 116 can be exposed. Theinsulator 120 can comprise, for example, SiO, SiN, SiON, Al₂O₃, or AlN.

Referring to FIG. 22(B), the third ohmic layer 130 is formed on theexposed portion of the second semiconductor layer 116. The thirdelectrode 140 can be formed on the insulator 120 and on the third ohmiccontact layer 130. That is, the third electrode 140 can be conformallyformed on the top surface and sidewall of the first light emitting chip110. In an exemplary embodiment, the third electrode 140 can comprise amaterial with a high reflectivity such as, for example, Ag or Al. Theohmic contact layer 130 can comprise, for example, at least one ofindium tin oxide (ITO), Zn, ZnO, Ag, Ti, Al, Au, Ni, In₂O₃, SnO₂, Cu, Wor Pt. A heat treatment using a heat of about 400° C. can be performedto activate the third ohmic contact layer 130. The third ohmic contactlayer 130 disposed between the third electrode 140 and the secondsemiconductor layer 116 can increase the current spreading.

Referring to FIG. 23(A), the second substrate 200 can be formed on thethird electrode 140 with the intermediate layer 210 disposedtherebetween. As such, the first and second substrates 100 and 200 arebonded with each other. The second substrate 200 can be a conductivesubstrate. The second substrate 200 may comprise, for example, Si,strained Si, Si alloy, SOI, SiC, SiGeC, Ge, Ge alloy, GaAs, InAs, orIII-V semiconductor. The intermediate layer 210 can comprise, forexample, at least one of Au, Ag, Pt, Ni, Cu, Sn, Al, PB, Cr, or Ti. Theintermediate layer 210 can have a lower reflective index than the thirdelectrode 140. When the intermediate layer 210 comprises Au, the firstand second substrates 100 and 200 can be bonded with each other by athermal process using heat of about 200° C. to about 450° C. In anexemplary embodiment, a pressure process can be added in the thermalprocess.

Referring to FIG. 23(B), the first substrate 100 is removed from thefirst semiconductor layer 112. In an exemplary embodiment, laser can beused to remove the first substrate 100. For example, the laser melts thebuffer layer or n-GaN formed between the first substrate 100 and thefirst semiconductor layer 112 such that the first substrate 100 can beseparated from the first semiconductor layer 112. In an exemplaryembodiment, a thinning process including a CMP, grinding, or etch backprocess can be performed before removing the first substrate 100 toprevent damage to the first light emitting device 110.

Referring to FIG. 24, the first ohmic contact layer 142 is formed on thefirst semiconductor layer 112. The first electrode 150 is formed on thefirst ohmic contact layer 142. In an exemplary embodiment, the firstelectrode 150 can be formed on near an edge of the first ohmic contactlayer 142 such that the second light emitting chip 160 can be disposedon the first ohmic contact layer 142 without contacting the firstelectrode 150. The first ohmic contact layer 142 may comprise, forexample, ITO, Zn, ZnO, Ag, Ti, Al, Au, Ni, In₂O₃, SnO₂, Cu, W or Pt. Thefirst electrode 150 may comprise, for example, ITO, Cu, Ni, Cr, Au, Ti,Pt, Al, V, W, Mo or Ag. The first ohmic contact layer 142 can increasethe current spreading passing though the first and second light emittingchips 110 and 160.

Referring to FIG. 25(A), the third preliminary semiconductor layer 162 ais formed on a third substrate 101. A fourth preliminary semiconductorlayer 166 a is formed on the third preliminary semiconductor layer 162 awith a second preliminary active layer 164 a disposed therebetween. Thesecond preliminary ohmic contact layer 168 a is formed on the fourthpreliminary semiconductor layer 166 a.

Referring FIG. 25(B), the second light emitting chip 160 is formed bypatterning the third preliminary semiconductor layer 162 a, the fourthpreliminary semiconductor layer 166 a, the second preliminary activelayer 164 a, and the second preliminary active layer 164 a. In anexemplary embodiment, the first light emitting chip 110 except for aportion overlapped with the first electrode 150 has a substantially thesame shape as the second light emitting chip 160.

Referring to FIG. 26, the second light emitting chip 160 disposed on thethird substrate 101 is bonded together with the first light emittingchip 110 disposed on the second substrate 200. That is, the first ohmiccontact layer 142 disposed on the first light emitting chip 110 contactsthe second ohmic contact layer 168 disposed the second light emittingchip 160. As such, the first semiconductor layer 112 and the fourthsemiconductor layer 166 are electrically connected thorough the firstand second ohmic contact layers 142 and 168.

Referring to FIG. 27, the third substrate 101 is removed from the secondlight emitting chip 160. The second electrode 170 can be formed on thethird semiconductor layer 162.

Exemplary embodiments of the present invention provide a light emittingdevice having at least two LED chips stacked one over another. The lightemitting device can operate on AC power. The two LED chips areelectrically connected with a conductive material disposed therebetween.As such, a number of the electrodes and wires connecting the two LEDchips in the light emitting device can be minimized.

Although the exemplary embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the present invention should not be limited to thoseprecise embodiments and that various other changes and modifications maybe affected therein by one of ordinary skill in the related art withoutdeparting from the scope or spirit of the invention. All such changesand modifications are intended to be included within the scope of theinvention as defined by the appended claims.

1. A semiconductor device comprising: a first light emitting chip, thefirst light emitting chip having a first semiconductor layer, a secondsemiconductor layer, and a first active layer disposed therebetween; asecond light emitting chip disposed on the first light emitting chip,the second light emitting chip having a third semiconductor layer, afourth semiconductor layer, and a second active layer disposedtherebetween; and a conductive layer disposed between the firstsemiconductor layer and the fourth semiconductor layer, the firstsemiconductor layer and the fourth semiconductor layer having differentconductivity types.
 2. The semiconductor device of claim 1, furthercomprising a first electrode disposed on the conductive layer, a secondelectrode disposed on the third semiconductor layer, and a thirdelectrode disposed on the second semiconductor layer.
 3. Thesemiconductor device of claim 2, wherein the second electrode and thethird electrode are electrically connected.
 4. The semiconductor deviceof claim 1, wherein the second semiconductor layer is disposed on asubstrate.
 5. The semiconductor device of claim 4, wherein the substratecomprising at least one of a semiconductor material or a conductivematerial.
 6. The semiconductor device of claim 1, wherein the conductivelayer is transparent.
 7. The semiconductor device of claim 1, whereinthe conductive layer is reflective.
 8. The semiconductor device of claim2, wherein the third electrode is reflective.
 9. The semiconductordevice of claim 8, wherein the third electrode includes a reflectiveside wall.
 10. The semiconductor device of claim 7, wherein the thirdelectrode is flat.
 11. The semiconductor device of claim 1, furthercomprising vias disposed between the fourth semiconductor layer and theconductive layer.
 12. The semiconductor device of claim 1, wherein thesecond light emitting chip is a vertical type emitting chip.
 13. Thesemiconductor device of claim 1, further comprising a third lightemitting chip including a fifth semiconductor layer, the fifthsemiconductor layer disposed on the third semiconductor layer, the fifthsemiconductor layer and the third semiconductor layer having differentconductive types.
 14. The semiconductor device of claim 1, furthercomprising a third light emitting chip including a fifth semiconductorlayer, the fifth semiconductor layer disposed on the third semiconductorlayer, the fifth semiconductor layer and the third semiconductor layerhaving the same conductive type.
 15. The semiconductor device of claim1, wherein the first and second light emitting chips configured to bealternately energized on respective alternating halves of an AC waveformto emit light.
 16. The semiconductor device of claim 1, wherein acontour of the first light emitting chip overlapping the second lightemitting chip is substantially the same as a contour of the second lightemitting chip.